Documentation

BizDay is a REST API for workday calculations. It answers questions like “is this date a workday?”, “what’s the next workday?”, and “how many workdays between two dates?” for 30+ countries.

Authentication

All API requests (except /v1/countries) require an API key. Pass it via the Authorization header:

curl "https://api.bizday.dev/v1/check?date=2026-03-05&country=US" \
  -H "Authorization: Bearer wday_your_api_key"

You can also pass the key as a query parameter:

curl "https://api.bizday.dev/v1/check?date=2026-03-05&country=US&api_key=wday_your_api_key"

Making Requests

All endpoints accept GET requests with query parameters. Dates must be in YYYY-MM-DD format. Country codes must be ISO 3166-1 alpha-2 (e.g. GB, US, DE).

Response Format

All responses follow a consistent JSON envelope:

// Success
{
  "success": true,
  "data": { ... },
  "meta": {
    "country": "GB",
    "requested_date": "2026-03-05",
    "cached": false,
    "timestamp": "2026-03-05T10:23:41.000Z"
  }
}

// Error
{
  "success": false,
  "error": {
    "code": "INVALID_DATE",
    "message": "Date must be in YYYY-MM-DD format.",
    "docs": "https://bizday.dev/docs/errors#INVALID_DATE"
  }
}

GET /v1/check

Check if a specific date is a workday in a given country.

Parameters

{
  "success": true,
  "data": {
    "date": "2026-12-25",
    "country": "GB",
    "is_workday": false,
    "reason": "public_holiday",
    "holiday": {
      "name": "Christmas Day",
      "local_name": "Christmas Day",
      "type": "Public"
    }
  }
}

GET /v1/next

Find the next (or previous) workday from a given date.

Parameters

{
  "success": true,
  "data": {
    "from_date": "2026-12-24",
    "country": "GB",
    "direction": "next",
    "workday": "2026-12-29"
  }
}

GET /v1/add

Add (or subtract) a number of workdays to a date, skipping weekends and holidays.

Parameters

{
  "success": true,
  "data": {
    "start_date": "2026-03-05",
    "country": "US",
    "workdays_added": 10,
    "result_date": "2026-03-19",
    "weekends_skipped": 4,
    "holidays_skipped": []
  }
}

GET /v1/between

Count the number of workdays between two dates.

Parameters

{
  "success": true,
  "data": {
    "country": "DE",
    "start_date": "2026-03-01",
    "end_date": "2026-03-31",
    "workdays": 21,
    "weekends": 9,
    "holidays": 1,
    "holiday_list": [
      { "date": "2026-04-03", "name": "Good Friday" }
    ]
  }
}

GET /v1/countries

List all supported countries. This endpoint does not require authentication.

{
  "success": true,
  "data": {
    "countries": [
      { "code": "AU", "name": "Australia" },
      { "code": "AT", "name": "Austria" },
      ...
    ],
    "count": 30
  }
}

Error Codes

All errors include a machine-readable code and a human-readable message.

Rate Limits

Rate limits are applied per API key on a monthly basis. Every response includes these headers:

Supported Countries

Holiday data is synced weekly from authoritative sources. Currently supported: